Mod+x misbehaving #77

I don't have a good reproducible testcase available right now, but it seems Mod+x behavior isn't always behaving well. To look into.

I had a scenario where:

• top-level split vertically
• left split in three horizontally
• bottom split vertically
• right side tabbed

Hitting mod+x on the 'middle' of the 3 horizontally split frames led to a spurious header over the H[T[x] T[x x x x]]

What do you have Mod+x bound to?

split none (aka unsplit)

Hrm it seems I was using 'horizontally'/'vertically' differently from Sway: apparently sway calls two windows that are next to each other 'horizontally split' and windows that are above/under each other 'vertically split'. I guess we should follow that (though it's counter-intuitive to me).

recipe for reproducing:

• start volare
• split horizontally
• unsplit
• split horizontally
• split the left side vertically
• mod+x the right side

This leaves a situation where the 'top-level' vertically split window has a titlebar (showing 'V[T[] T[]]'), but both split windows as well (showing nothing). Also, Mod+w no longer 'wraps around' correctly.

Another error case (perhaps we'll have to split this issue...):

• start volare
• split vertically
• split vertically
• start terminals on all 3 tiles
• unsplit the bottom tile

I think what we'd want to happen in this case is that the top tile remains as-is, and a tabbed container is introduced to hold the bottom two terminals. Instead, the bottom terminal is added to the top-level vertical split.